Syndecan-4 Is Essential for Development of Concentric Myocardial Hypertrophy via Stretch-Induced Activation of the Calcineurin-NFAT Pathway

Sustained pressure overload leads to compensatory myocardial hypertrophy and subsequent heart failure, a leading cause of morbidity and mortality. Further unraveling of the cellular processes involved is essential for development of new treatment strategies. We have investigated the hypothesis that the transmembrane Z-disc proteoglycan syndecan-4, a co-receptor for integrins, connecting extracellular matrix proteins to the cytoskeleton, is an important signal transducer in cardiomyocytes during development of concentric myocardial hypertrophy following pressure overload. Echocardiographic, histochemical and cardiomyocyte size measurements showed that syndecan-4−/− mice did not develop concentric myocardial hypertrophy as found in wild-type mice, but rather left ventricular dilatation and dysfunction following pressure overload. Protein and gene expression analyses revealed diminished activation of the central, pro-hypertrophic calcineurin-nuclear factor of activated T-cell (NFAT) signaling pathway. Cardiomyocytes from syndecan-4−/−-NFAT-luciferase reporter mice subjected to cyclic mechanical stretch, a hypertrophic stimulus, showed minimal activation of NFAT (1.6-fold) compared to 5.8-fold increase in NFAT-luciferase control cardiomyocytes. Accordingly, overexpression of syndecan-4 or introducing a cell-permeable membrane-targeted syndecan-4 polypeptide (gain of function) activated NFATc4 in vitro. Pull-down experiments demonstrated a direct intracellular syndecan-4-calcineurin interaction. This interaction and activation of NFAT were increased by dephosphorylation of serine 179 (pS179) in syndecan-4. During pressure overload, phosphorylation of syndecan-4 was decreased, and association between syndecan-4, calcineurin and its co-activator calmodulin increased. Moreover, calcineurin dephosphorylated pS179, indicating that calcineurin regulates its own binding and activation. Finally, patients with hypertrophic myocardium due to aortic stenosis had increased syndecan-4 levels with decreased pS179 which was associated with increased NFAT activation. In conclusion, our data show that syndecan-4 is essential for compensatory hypertrophy in the pressure overloaded heart. Specifically, syndecan-4 regulates stretch-induced activation of the calcineurin-NFAT pathway in cardiomyocytes. Thus, our data suggest that manipulation of syndecan-4 may provide an option for therapeutic modulation of calcineurin-NFAT signaling

Combinatorial targeting and discovery of ligand-receptors in organelles of mammalian cells

Phage display screening allows the study of functional protein–protein interactions at the cell surface, but investigating intracellular organelles remains a challenge. Here we introduce internalizing-phage libraries to identify clones that enter mammalian cells through a receptor-independent mechanism and target-specific organelles as a tool to select ligand peptides and identify their intracellular receptors. We demonstrate that penetratin, an antennapedia-derived peptide, can be displayed on the phage envelope and mediate receptor-independent uptake of internalizing phage into cells. We also show that an internalizing-phage construct displaying an established mitochondria-specific localization signal targets mitochondria, and that an internalizing-phage random peptide library selects for peptide motifs that localize to different intracellular compartments. As a proof-of-concept, we demonstrate that one such peptide, if chemically fused to penetratin, is internalized receptor-independently, localizes to mitochondria, and promotes cell death. This combinatorial platform technology has potential applications in cell biology and drug development

Anti-calmodulins and Tricyclic Adjuvants in Pain Therapy Block the TRPV1 Channel

Ca2+-loaded calmodulin normally inhibits multiple Ca2+-channels upon dangerous elevation of intracellular Ca2+ and protects cells from Ca2+-cytotoxicity, so blocking of calmodulin should theoretically lead to uncontrolled elevation of intracellular Ca2+. Paradoxically, classical anti-psychotic, anti-calmodulin drugs were noted here to inhibit Ca2+-uptake via the vanilloid inducible Ca2+-channel/inflamatory pain receptor 1 (TRPV1), which suggests that calmodulin inhibitors may block pore formation and Ca2+ entry. Functional assays on TRPV1 expressing cells support direct, dose-dependent inhibition of vanilloid-induced 45Ca2+-uptake at µM concentrations: calmidazolium (broad range)≥trifluoperazine (narrow range)>chlorpromazine/amitriptyline>fluphenazine>>W-7 and W-13 (only partially). Most likely a short acidic domain at the pore loop of the channel orifice functions as binding site either for Ca2+ or anti-calmodulin drugs. Camstatin, a selective peptide blocker of calmodulin, inhibits vanilloid-induced Ca2+-uptake in intact TRPV1+ cells, and suggests an extracellular site of inhibition. TRPV1+, inflammatory pain-conferring nociceptive neurons from sensory ganglia, were blocked by various anti-psychotic and anti-calmodulin drugs. Among them, calmidazolium, the most effective calmodulin agonist, blocked Ca2+-entry by a non-competitive kinetics, affecting the TRPV1 at a different site than the vanilloid binding pocket. Data suggest that various calmodulin antagonists dock to an extracellular site, not found in other Ca2+-channels. Calmodulin antagonist-evoked inhibition of TRPV1 and NMDA receptors/Ca2+-channels was validated by microiontophoresis of calmidazolium to laminectomised rat monitored with extracellular single unit recordings in vivo. These unexpected findings may explain empirically noted efficacy of clinical pain adjuvant therapy that justify efforts to develop hits into painkillers, selective to sensory Ca2+-channels but not affecting motoneurons

The solute carrier SLC7A1 may act as a protein transporter at the blood-brain barrier

Despite extensive research, targeted delivery of substances to the brain still poses a great challenge due to the selectivity of the blood-brain barrier (BBB). Most molecules require either carrier- or receptor-mediated transport systems to reach the central nervous system (CNS). These transport systems form attractive routes for the delivery of therapeutics into the CNS, yet the number of known brain endothelium-enriched receptors allowing the transport of large molecules into the brain is scarce. Therefore, to identify novel BBB targets, we combined transcriptomic analysis of human and murine brain endothelium and performed a complex screening of BBB-enriched genes according to established selection criteria. As a result, we propose the high-affinity cationic amino acid transporter 1 (SLC7A1) as a novel candidate for transport of large molecules across the BBB. Using RNA sequencing and in situ hybridization assays, we demonstrated elevated SLC7A1 gene expression in both human and mouse brain endothelium. Moreover, we confirmed SLC7A1 protein expression in brain vasculature of both young and aged mice. To assess the potential of SLC7A1 as a transporter for larger proteins, we performed internalization and transcytosis studies using a radiolabelled or fluorophore-labelled anti-SLC7A1 antibody. Our results showed that SLC7A1 internalised a SLC7A1-specific antibody in human colorectal carcinoma (HCT116) cells. Moreover, transcytosis studies in both immortalised human brain endothelial (hCMEC/D3) cells and primary mouse brain endothelial cells clearly demonstrated that SLC7A1 effectively transported the SLC7A1-specific antibody from luminal to abluminal side. Therefore, here in this study, we present for the first time the SLC7A1 as a novel candidate for transport of larger molecules across the BBB

Water-pipe smoke condensate increases the internalization of Mycobacterium Bovis of type II alveolar epithelial cells (A549)

Background: Tuberculosis (TB) is a major global health problem, and there is an association between tobacco smoke and TB. Water pipe smoking has become an increasing problem not only in Middle Eastern countries but also globally because users consider it as safer than cigarettes. The presence of high levels of toxic substances in water-pipe smoke may be a predisposing factor that enhances the incidence of pulmonary disorders. For example, uncontrolled macropinocytosis in alveolar epithelial cells following exposure to water-pipe smoke may predispose subjects to pulmonary infection. Here, we studied the effects of water-pipe condense (WPC) on the internalization of Mycobacterium Bovis BCG by macropinocytosis in the alveolar epithelial cell line A549. Methods: A549 cells were exposed to WPC (4 mg/ml) for 24, 48, 72 and 96 h. Cell viability was studied using the methyl thiazolyldipenyl-tetrazolium bromide (MTT) reduction assay and proliferation by bromodeoxyUridine (BrdU) incorporation. Cells were exposed to FITC-Dextran (1 mg/ml) (as a control) and FITC-BCG (MOI = 10) for 20 min at 37 ° Cbeforecellswere collected and the uptake of BCG-FITC determined by flow cytometry. Similar experiments were performed at 4 ° Casacontrol . The Rho-associated protein kinase (ROCK) inhibitor Y-27632 (1 μ M) was used to assess the mechanism by which WPC enhanced BCG uptake. Results: WPC (4 mg/ml) increased the uptake of BCG-FITC after 72 (1.3 ± 0.1 fold, p < 0.05) and 96 (1.4 ± 0.05 fold, p < 0.05) hours. No effect on BCG-FITC uptake was observed at 24 or 48 h. WPC also significantly increased the uptake of FITC-Dextran (2.9 ± 0.3 fold, p < 0.05) after 24 h. WPC significantly decreased cell viability after 24 (84 ± 2%, p < 0.05), 48 (78±, 3%, p < 0.05), 72 (64 ± 2%, p < 0.05) and 96 h (45 ± 2%, p < 0.05). Y-27632 completely attenuated the increased uptake of BCG by WPC. Cell proliferation showed a decreasing trend in a time-dependent manner with WPC exposure. Conclusion: WPC exposure increased epithelial cell endocytosis activity and death as well as enhancing their capacity for macropinocytosis. Our in vitro data indicates possible harmful effects of WPC on the ability of lung epithelial cells to phagocytose mycobacterium

Syndecan-4 mediates the cellular entry of adeno-associated virus 9

Due to their low pathogenicity, immunogenicity, and long-term gene expression, adeno-associated virus (AAV) vectors emerged as safe and efficient gene delivery tools, over-coming setbacks experienced with other viral gene delivery systems in early gene therapy trials. Among AAVs, AAV9 can translocate through the blood-brain barrier (BBB), making it a promising gene delivery tool for transducing the central nervous system (CNS) via systemic administration. Recent reports on the shortcomings of AAV9-mediated gene delivery into the CNS require reviewing the molecular base of AAV9 cellular biology. A more detailed understanding of AAV9’s cellular entry would eradicate current hurdles and enable more efficient AAV9-based gene therapy approaches. Syndecans, the transmembrane family of heparan-sulfate proteoglycans, facilitate the cellular uptake of various viruses and drug delivery systems. Utilizing human cell lines and syndecan-specific cellular assays, we assessed the involvement of syndecans in AAV9’s cellular entry. The ubiquitously expressed isoform, syndecan-4 proved its superiority in facilitating AAV9 internalization among syndecans. Introducing syndecan-4 into poorly transducible cell lines enabled robust AAV9-dependent gene transduction, while its knockdown reduced AAV9’s cellular entry. Attachment of AAV9 to syndecan-4 is mediated not just by the polyanionic heparan-sulfate chains but also by the cell-binding domain of the extracellular syndecan-4 core protein. Co-immunoprecipitation assays and affinity proteomics also confirmed the role of syndecan-4 in the cellular entry of AAV9. Overall, our findings highlight the universally expressed syndecan-4 as a significant contributor to the cellular internalization of AAV9 and provide a molecular-based, rational explanation for the low gene delivery potential of AAV9 into the CNS